Although, sendmail would still run without the CRL File and just complain about it missing. A quick way to include it in the sendmail configuration is to download revoke.crl from cacert.org, add the below option in sendmail.mc and rebuild the sendmail conf file as below.

Download revoke.crl:

# cd /usr/share/ssl/certs# wget http://www.cacert.org/revoke.crl

Add the below line to "/etc/mail/sendmail.mc" just below the "confSERVER_KEY":

define(`confCRL', `/usr/share/ssl/certs/revoke.crl')

Rebuild sendmail conf by running make:

# cd /etc/mail# make

Check sendmail.cf with the revoke.crl listed as below:

O CRLFile=/usr/share/ssl/certs/revoke.crl

Now restarting sendmail should not complain about the missing Certificate Revocation List (CRL) File.